Coriolis mass flow sensors having different resonant frequencies

ABSTRACT

A flow measurement system includes two or more flow sensors that may operate simultaneously and a plurality of connected flow paths for flow of fluids. Each flow sensor is positioned along a different flow path of the plurality of connected flow paths and includes at least one flow tube and a support that clamps the flow tube. The flow tube of each flow sensor has a different resonant frequency so that cross-talk between the flow sensors can be reduced or eliminated. In some embodiments, the flow tube of each flow sensor has a different tube length, wall thickness, material, and/or weight. The flow measurement system can also include one or more pumps for pumping fluid into the flow sensors and a dampener arranged between a pump and a corresponding flow sensor for mitigating interference on the flow sensor from operation of the pump.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/846,061, “Coriolis Mass Flow Sensors Having Different ResonantFrequencies,” filed Apr. 10, 2020. The subject matter of all of theforegoing is incorporated herein by reference in its entirety.

BACKGROUND Field of the Disclosure

The present disclosure generally relates to Coriolis mass flow sensors(also referred to as “flow sensors” or “flow cells”), and specificallyto flow sensors that have different resonant frequencies.

Description of the Related Arts

A flow process system, e.g., a process skid, usually includes a numberof similar or even identical flow sensors. Cross-talk is a phenomenonwhere two or more flow sensors having identical operating resonantfrequencies which will cause harmonic interference with each other. Thecross-talk can include electrical cross-talk, mechanical cross-talk,and/or fluid pulsation based cross-talk. The cross-talk can causeinaccurate measurement by the flow sensors. A flow process system canalso include pumps. Operation of the pumps can interfere with vibrationwithin the flow sensors, which also causes inaccurate measurement by theflow sensors.

Conventionally, heavy enclosures are used in flow sensors to mitigatecross-talk and pump interference. These enclosures are usually made frommetal, e.g., stainless steel. However, metal enclosures can be expensiveand are not suitable for single use/disposable applications. Also,sterilization of flow sensors having metal enclosures is typically doneby using chemicals, which is not effective and can cause malfunction ofthe flow sensors. Thus, improved technologies for mitigating cross-talkand pump interference are needed.

SUMMARY

Embodiments relate to a flow measurement system including a plurality offlow sensors and a plurality of connected flow paths for flow of fluids.The flow sensors can operate simultaneously to measure flow rates and/ordensities of different fluids. Each flow sensor is positioned along atleast one of the connected flow paths. Each flow sensor includes one ormore flow tubes and a support clamping the flow tubes. The support canbe cast around the flow tubes or formed around the flow tubes throughover-molding. The flow tubes of different flow sensors have differentresonant frequencies as a result of a difference in their tube lengths,materials, wall thicknesses, weights, other parameters relating toresonant frequency, or some combination thereof. Thus, cross-talkbetween the flow sensors can be reduced or eliminated, even without theuse of metal enclosures. In some embodiments, each flow sensor includesa plastic enclosure and can be sterilized by using Gamma irradiation.

The flow measurement system can also include at least one pump thatpumps a fluid into one or more of the flow sensors. The pump may operateat a frequency that is similar to or same as the resonant frequency ofthe flow sensor and, therefore, interfere with the operation of the flowsensor. To mitigate this interference, a dampener is positioned betweenthe pump and the flow sensor. The fluid flows through the dampenerbefore it enters the flow sensor. The dampener mitigates vibration ofthe fluid caused by the pump.

In some embodiments, each flow sensor includes a plastic enclosure andcan be sterilized by using Gamma irradiation.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the embodiments can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings.

FIG. 1 is a diagram illustrating a flow measurement system containing aplurality of flow sensors, in accordance with an embodiment.

FIG. 2 is a perspective view of a flow sensor including U-shaped flowtubes, in accordance with an embodiment.

FIG. 3 illustrates a tube length of U-shape flow tubes, in accordancewith an embodiment.

FIG. 4 illustrates a wall thickness of U-shaped flow tubes, inaccordance with an embodiment.

FIG. 5 illustrates attachments mounted on U-shaped flow tubes, inaccordance with an embodiment.

FIG. 6A illustrates a flow sensor including a V-shaped flow tube, inaccordance with an embodiment.

FIG. 6B illustrates a flow sensor system including the flow sensor, inaccordance with an embodiment.

FIG. 7 illustrates a tube length of a flow sensor including a V-shapeflow tube, in accordance with an embodiment.

FIG. 8 illustrates an attachment mounted on a V-shaped flow tube, inaccordance with an embodiment.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles, or benefits touted, of the disclosure described herein.

DETAILED DESCRIPTION

Embodiments relate to a flow measurement system including a plurality offlow sensors, at least one pump, and at least one dampener that arepositioned along connected flow paths. Each flow sensor includes atleast one flow tube, a support clamping the flow tube, and a plasticenclosure. The flow tube of each flow sensor has a different resonantfrequency, so that cross-talk among the flow sensors can be reduced oreven eliminated. The flow sensor can be calibrated during manufacturingand calibration factors generated during the calibration can be storedin a memory chip of the flow sensor for adjusting flow measurements bythe flow sensor during operation. The flow sensor can be sterilized,e.g., by using Gamma irradiation, after the calibration. Furthercalibration or sterilization by a user of the flow meter may not berequired. Each dampener can be installed between a pump and one of theflow sensors to mitigate interference from the operation of the pump onthe operation of the flow sensor.

FIG. 1 is a diagram illustrating a flow measurement system 100containing a plurality of flow sensors 110, 120, and 130, in accordancewith an embodiment. The flow measurement system 100 also includes twopumps 113 and 123, three controllers 115, 125, and 135, three dampeners117, 127, and 137, and a mixing manifold 140. In other embodiments, theflow measurement system 100 may include additional, fewer, or differentcomponents. For instance, the flow measurement system 100 can includemore flow sensors, pumps, or dampeners. The flow measurement system 100can be a part of a process skid, e.g., a biopharmaceutical orpharmaceutical skid.

A first fluid 150 and a second fluid 160 enter the flow measurementsystem 100. The flow measurement system includes connected flow pathsfor flow of the first fluid 150 and the second fluid 160. The firstfluid enters the pump 113, which pumps the first fluid 150 into thedampener 117, and then flows from the dampener 117 to the flow sensor110. The second fluid 160 enters the pump 123, which pumps the secondfluid 160 into the dampener 127, and then flows from the dampener 127 tothe flow sensor 120. The flow sensor 110 measures flow characteristics(e.g., mass flow rate, volumetric flow rate, flow density, etc.) of thefirst fluid 150, the flow sensor 120 measures flow characteristics ofthe second fluid 160.

The flow path of the first fluid 150 (also referred to as “first flowpath”) and the flow path of the second fluid 160 (also referred to as“second flow path”) are connected at the mixing manifold 140, where athird fluid 170 is generated and a third flow path starts. The thirdfluid 170 can be a mixture or blend of the first fluid 150 and thesecond fluid 160. In some embodiments, the mixing manifold 140 includesanother fluid or matter that can be mixed or react with the first fluid150 and the second fluid 160 to generate the third fluid 170. The mixingmanifold 140 may include a pump that pumps the third fluid 170 to thedampener 137. The third fluid flows from the dampener 137 to the flowsensor 130. The flow sensor 130 measures flow characteristics of a thirdfluid 170.

The flow sensors 110, 120, and 130 can operate simultaneously. Each flowsensor includes a pair of flow tubes having different characteristics(e.g., different tube length, different wall thickness, differentmaterial, different weight, or some combination thereof) from the flowtubes of the other flow sensors and, thereby, has a different resonantfrequency. Due to the different resonant frequencies, cross-talk betweenthe flow sensors 110, 120, and 130 can be reduced or even eliminated. Asone example, the flow tubes of each flow sensor may be made of adifferent material. Examples of the material includes stainless steel,Polyetheretherketone (PEEK), Perfluoroalkoxy alkanes (PFAs),Polyvinylidene difluoride (PVDF), Polytetrafluoroethylene (PTFE), andFluorinated ethylene propylene (FEP). Other than the differentialresonant frequencies, the flow sensors 110, 120, and 130 may be similarto or same as each other.

In some embodiments, at least two of the flow sensors 110, 120, and 130can have an identical flow rate range. A flow rate range of a flowsensor is a range of flow rates that the flow sensor measures. The flowrate range can depend on the inner diameter of one or more flow tubes ofthe flow sensor. For instance, when the inner diameter of the flow tubeis in the range from 0.1 mm to 0.3 mm, the flow rate range of the flowsensor is 0.05 g/min to 5 g/min. When the inner diameter of the flowtube is in the range from 0.3 mm to 0.9 mm, the flow rate range of theflow sensor is 0.25 g/min to 50 g/min. When the inner diameter of theflow tube is in the range from 5.5 mm to 6.5 mm, the flow rate range ofthe flow sensor is 15 g/min to 3 kg/min. When the inner diameter of theflow tube is in the range from 7.8 mm to 12.5 mm, the flow rate range ofthe flow sensor is 90 g/min to 20 kg/ min. When the inner diameter ofthe flow tube is in the range from 15 mm to 60 mm, the flow rate rangeof the flow sensor is 1 kg/min to 250 kg/min.

Taking the flow sensor 110 for example, the flow sensor 110 includes twoflow tubes 119 that provide a flow path of the first fluid 150 in theflow sensor 110. The flow tubes 119 can vibrate, e.g., as driven bymagnets and coils. As the first fluid 150 flow through the flow tubes119, Coriolis forces produce a twisting vibration of the flow tubes 119,resulting in a phase shift of the flow tubes 119. Also, the first fluid150 changes the resonant frequency of the flow tubes 119. The flowsensor 110 generates signals, e.g., electrical signals, that representthe phase shift and/or change in its resonant frequency. The signals aresent to the controller 115 through an interface connector on the flowsensor 110.

In some embodiments, the flow sensor 110 also includes a memory chip(not shown in FIG. 1) that stores calibration information that can beused to adjust flow measurements made by the flow sensor 100. Forinstance, the calibration information can include one or more flow ratecalibration factors. Each flow rate calibration factor indicates adifference between a flow rate measured by the flow sensor 110 and areference flow rate and can be used to adjust flow rates measured by theflow sensor 110. The calibration information can also include one ormore flow density calibration factors. Each flow density calibrationfactor indicates a difference between a flow density measured by theflow sensor 110 and a reference flow density and can be used to adjustflow densities measured by the flow sensor 110. The calibrationinformation can be determined during manufacturing.

The flow sensor 110 can include a temperature probe (not shown inFIG. 1) that measures temperatures of the first fluid 150. The measuredtemperatures can be used to adjust flow rates and/or densities measuredby the flow sensor 100.

In the embodiment of FIG. 1, the flow sensors 110, 120, and 130 includeU-shaped flow tubes. Flow sensors in other embodiments can include flowtubes of other forms, such as V-shaped. More details about flow sensorsare described below in conjunction with FIGS. 2-8.

The controller 115 receives signals from the flow sensor 110 andconducts flow analysis based on the signals. The flow analysis includes,for example, determination of flow rate based on signals representingphase shift of the flow tubes 119, determination of flow density basedon signals representing change in resonant frequency of the flow tubes119, detection of bubbles in the first fluid 150 based on change in flowdensity, determination of other flow characteristics of the first fluid150, or some combination thereof.

The controller 115 can read out the calibration information from thememory chip of the flow sensor 110 and use the calibration informationin its flow analysis. For example, the controller uses a flow ratecalibration factor to determine a flow rate of the fluid or uses a flowdensity calibration factor to determine a density of the fluid. Thecontroller 115 can also receive temperature information from thetemperature probe and use the temperature information to dynamicallyadjust the flow analysis. For instance, the controller can input thetemperature information into a model and the model can output adjustedflow rate and/or flow density.

In some embodiments, the controller is a flow transmitter. In FIG. 1,each flow sensor is connected to a respective controller for flowanalysis. The flow sensor 110, cradle (usually made of stainless steel)of the flow sensor, and the controller 115 together can be referred toas a flow meter or a flow meter system.

In some embodiments, the pumps 113 and 123 are identical and thedampener 117 and 127 are identical. Taking the pump 113 as an example,it can be a diaphragm based pulsating pump (such as Quattroflow ModelSU-1200 Pump, SU-4400 Pump, SU-150 Pump, SU-30 Pump and SU-5050 Pump,etc), a peristaltic pump, or other types of pumps. The flow sensor 110measures flow characteristics based on vibration caused by the fluidflowing through the flow sensor. However, the pump 113 can operate at afrequency that is similar to or same as the resonant frequency of theflow sensor 110 and cause the first fluid 150 to vibrate or pulsate.This can degrade operation of the flow sensor 110, such as inaccuratemeasurement, erratic report, etc. The pulsating operation of the pump113 may also degrade operation of the flow sensors 120 and 130, which isreferred to destructive harmonic interference

The dampener 117 mitigates the destructive harmonic interference fromthe pump 113 on the flow sensor 110. As the first fluid 150 flows thoughthe dampener 117, the vibration of the first fluid 150 at the frequencyof the pump 113 can be reduced or even eliminated.

FIG. 2 is a perspective view of a flow sensor 200 including U-shapedflow tubes 210, in accordance with an embodiment. The flow sensor 200can be an embodiment of one of the flow sensors 110, 120, and 130 inFIG. 1. In addition to the flow tubes 210 (individually referred as“flow tube 210”), the flow sensor 200 also includes a support 220 forthe flow tubes, an electromagnetic assembly 230, two flow pathassemblies, an electronic assembly, and an enclosure assembly. The flowsensor 200 may include additional, fewer, or different components. Forexample, the flow sensor 200 may include a temperature assembly formeasuring temperatures of the fluid or other sensor for measuring otherproperties of the fluid. FIG. 1 shows two flow tubes 210, but the flowsensor 200 may have one flow tube 210 or more than two flow tubes 210.

The flow tubes 210 allow the fluid to flow through them. The flow tubes210 vibrate as driven by the electromagnetic assembly 230, and theirvibration can be changed by the flow of the fluid. For instance, theflow tubes 210 can twist, which results in a phase shift. Also, thevibration resonant frequency can change. The mass flow rate of the fluidcan be directly determined based on the phase shift. The density of thefluid can be directly determined based on the change in vibrationresonant frequency. More details regarding the vibration of the flowtubes 210 and the determination of the flow rate and density aredescribed below in conjunction with the electromagnetic assembly 230.

As shown in FIG. 2, each flow tube 210 is a U-shaped tube having twoparallel tubular legs. The fluid flows into one of the tubular legs(referred as “inlet tubular leg”) and flows out from the other tubularleg (referred as “outlet tubular leg”). The flow tube 210 can have acurvilinear shape. One advantage of such a curvilinear shape is thatthere are no corners so there are no abrupt changes in direction alongthe flow path of the fluid. Accordingly, possible accumulation of solidsor any other contaminants inside the flow tubes 210 that may causeincreased pressure drop or cause the flow tubes 210 to dislodge from thesupport 220, which can result in particle contamination, is eliminated.In some other embodiments, the flow tube 210 can be in other shapes,such as V-shape, square, rectangular, triangular, elliptic, or straight.

Each flow tube 210 has a thin wall that is less than 1 mm thick, e.g.,0.05 mm to 0.60 mm thick. In some embodiments, the thickness of the wallis 5% to 16% of the outer diameter of the flow tube 210. The outerdiameter of the flow tube 210 can be in a range from 0.2 mm to 60 mm.With such a thin wall, the flow tube 210 has good accuracy even at lowfluid flow rates, such as 0.05-0.5 gm/min of mass flow rate or 0.05-0.5ml/min of volumetric flow rate.

In the embodiment of FIG. 2, the two flow tubes 210 are identical, i.e.,they have identical shape and dimensions. In some other embodiments, thetwo flow tubes 210 can be different. The flow tubes 210 may be made ofmetal (such as stainless steel) or a polymer material (such asPolyetheretherketone (PEEK), Perfluoroalkoxy polymers (PFAs),polyvinylidene difluoride (PVDF), Polytetrafluoroethylene (PTFE), andFluorinated ethylene propylene (FEP)).

The support 220 provides structural support for the flow tubes 210. Thesupport 220 may be fabricated by casting around the tubular legs of theflow tubes 210 or formed around the tubular legs of the flow tubes 210through over-molding. The support 220 includes tubular channels throughwhich the flow tubes 210 extend. The support 220 clamps the outersurface of the two tubular legs of each of the flow tubes 210 to holdthe flow tubes 210. Compared with other fabrication methods (e.g.,injection molding), pressure exerted on the flow tubes 210 andtemperature of the flow tubes 210 during the casting process is low sothat deformation of the flow tubes 210 can be avoided. More detailsregarding the casting are described below in conjunction with FIGS. 2-5.

The support 220 is a single integral piece. It may include integratedfeatures such as one or more port extensions 223 (individually referredas “port extension 223”) and isolation plates 225 (individually referredas “isolation plate 225”) to secure stability of the flow tubes 210. Theport extensions 223 clamp the tubular legs of the flow tubes 210. Aninner surface of each port extension 223 contacts the outer surface ofthe corresponding tubular leg. The isolation plates 225 connect adjacentport extensions 223. The isolation plates 225 can establish the boundaryconditions of vibration of the flow tubes 210 and maintain stability ofthe flow tubes 210. The flow tubes 210 can vibrate in opposite phases(referred as “anti-phase vibration”) similar to a tuning fork andvibrate together in unison (referred as “in-phase vibration”). Thenatural frequencies of the anti-phase vibration and in-phase vibrationcan be close or even identical, resulting in vibrational excitationenergy shared uncontrollably between the two vibrational modes, whichcauses instability of the flow tubes 210. The vibrational boundaryconditions created by the isolation plates 225 can separate the naturalfrequencies of the anti-phase vibration and in-phase vibration toprevent instability of the flow sensor 200. The dimensions and thicknessof the isolation plates 225 can be determined based on the frequencyresponse characteristics of the flow tubes 210. In some embodiments, theisolation plates 225 are integrated with the port extensions 223, bothof which are integrated with the support 220.

The electromagnetic assembly 230 drives vibration of the flow tubes 210.The electromagnetic assembly 230 includes three magnets, three coils,and two racks. The magnets are mounted on one of the two racks, which isattached on one of the flow tubes 210. The coils are mounted to theother rack, which is attached on the other flow tube 210. One of thethree coils, e.g., the coil in the middle, can receive an alternatingcurrent, e.g., from a controller (e.g., a flow transmitter) connected tothe flow sensor 200. The alternating current causes the magnetcorresponding to the coil to be attracted and repelled, thereby drivingthe flow tubes 210 to move towards and away from each another.

The electromagnetic assembly 230 also detects changes in the vibrationof the flow tubes 210 due to the flow of the fluid and outputselectrical signals that can be used to measure flow rate and density ofthe fluid. When the fluid flows through the flow tubes 210, Coriolisforces produce a twisting vibration of the flow tubes 210, which resultsin a phase shift. As the magnets and coils are mounted on the flowtubes, the phase shift can be captured by the magnets and coils, e.g.,represented by electrical signals of the coils and be used to determinea mass flow rate of the fluid.

The density of the fluid relates to the resonant frequency of the flowtubes 210. The density of the fluids can thereby be determined bymonitoring the change in the resonant frequency of the flow tubes 210.The resonant frequency of the flow tubes 210 depends at least on thedensity of the fluid present in the flow tubes 210 and the density of amaterial of the flow tubes 210.

The inlet flow path assembly provides a flow path for the fluid to flowinto the flow tubes 210. The inlet flow path assembly includes a Y block242A, a Y block adapter 244A, a tubing elbow 246A, a barb adapter 248A,and a hose barb 249A. The Y block 242A includes a top/inlet port on oneside and two bottom/outlet ports on the other side. It is formed with aninternal channel that connects the top port to the two bottom ports. Theoutlet ports of the Y block 242A are assembled and bonded onto the inlettubular legs of the flow tubes 210. The inlet port the Y block 242A isbonded to the Y block adapter 244A, which is bonded to one end of thetubing elbow 246A. The tubing elbow 246A forms an angle that is greaterthan 90° and provides a sweep turn to the fluid. Compared with a 90°turn, the fluid encounters a lower shear force when it flows through thetubing elbow 246A, which protects matters in the fluid from beingdamaged or destructively impacted. The matters in the fluid can beorganic matters, such as live cells, protein, virus, bacteria, etc. Theother end of the tubing elbow 246A is connected to the barb adapter248A, which is also connected to the hose barb 249A. The hose barb 249Acan be connected to a hose as required by the user when the userinstalls the flow sensor 200. More details about Y block and hose barbare described below in conjunction with FIGS. 8-10.

The outlet flow path assembly provides a flow path for the fluid to flowout from the flow tubes 210. Similar to the inlet flow path assembly,the outlet flow path assembly includes a Y block 242B, a Y block adapter244B, a tubing elbow 246B, a barb adapter 248B, and a hose barb 249B,which are connected similarly as the components of the inlet flow pathassembly described above. The hose barb 249B can be connected to anotherhose as required by the user when the user installs the flow sensor 200.

The hose barbs 249A and 249B are aligned in a straight line, asillustrated by the dashed line in FIG. 2. Such an alignment is desirablefor installing the flow sensor 200 into a system (e.g., a process skid)having a flow path arranged in a straight line. It is easier to installand plumb the flow sensor 200 in such a flow path. In other embodiments,the inlet and outlet flow path assemblies can have different componentsand different alignments for fitting in different flow paths.

The components of the inlet and outlet flow path assemblies can be madefrom a polymer (such as PEEK) by various processes, such as machining,extruding, injection molding, bending, etc. The components can be bondedtogether by using a glue, such as epoxy resin. These components and theglue can be sterilized by using Gamma irradiation, e.g., they arecompliant for Class VI Gamma sterilization up to 50 kGy.

In some embodiment, the flow sensor 200 may have inlet and outlet flowpath assemblies different from these in FIG. 2. For instance, each flowpath assembly has an end block, a barb adapter, and a hose barb. The endblock connects the flow tubes 210 to another flow device (such as ahose, tubing, or other types of plumbing). A channel is formed insidethe end block to allow the fluid to flow through it. The channel definesa flow path of the fluid inside the end block. The flow path of thefluid inside the end block has no right angle (90°) turns to avoid highshear force exerted on the fluid. The barb adapter may be similar to thebarb adapter 248A or 248B and can be glued on an inner surface of theend block. The hose barb can be similar to the hose barb 249A or 249B.The end block, barb adapter, and hose barb may form a straight line.

The electronic assembly facilitates storage and transmission of dataassociated with the flow sensor 200. The electronic assembly includes aprinted circuit board (PCB) 253, at least one memory chip (not shown inFIG. 2) mounted on the PCB 253, an interface cable 255 connected to thePCB 253, and an interface connector 257 connected to or assembled on thePCB 253.

The PCB 253 provides structural support for components mounted on it,such as the memory chip. The memory chip stores calibration informationof the flow sensor 200. The calibration information can be used toadjust a flow rate or density measured by the flow sensor 200. In someembodiments, the calibration information includes a plurality ofcalibration factors. Each calibration factor is for adjusting a flowrate, such as a low flow rate (e.g., about 1 liter/minute), medium flowrate (e.g., about 10 liter/minute), or high flow rate (e.g., from 20liter/minute to 200 liter/minute). The calibration information can beread out from the memory chip, e.g., by a flow transmitter, through theinterface connector 257.

The interface cable 255 connects the coils to the PCB 253. In FIG. 2,the interface cable 255 is also assembled onto the PCB 253 that providesstructural support to the interface cable 255. More details about theelectronic assembly are described below in conjunction with FIG. 7.

The enclosure assembly encloses the flow tube 210, the support 220, theelectromagnetic assembly 230, and the electronic assembly and providesstructural support to them. The enclosure assembly, shown in cut away inFIG. 2, includes an enclosure cup 260 and an enclosure lid 265. Theenclosure lid 265 can be mounted on the enclosure cup 260, e.g., throughbolts. In some embodiments, the enclosure assembly is made of a polymermaterial, e.g., polycarbonate or PEEK.

The flow tubes 210 and the support 220 can be integrated and disposed asone piece. For instance, the flow tubes 210 are removably mounted on theelectromagnetic assembly 230 and the support 220 are removably mountedon the enclosure lid 265, e.g., through mounting tabs and bolts. Thisway, the flow tubes 210 and the support 220 can be removed from theelectromagnetic assembly 230 and enclosure assembly, and new flow tubesand a new support can be mounted on the electromagnetic assembly 230 andenclosure assembly. In some embodiments, the flow tubes 210, the support220, and the electromagnetic assembly 230 are integrated to be one pieceand they can be disposed as one piece when needed. This design issuitable for disposable applications, such as applications where flowsensors need to be disposed to avoid contamination from fluids used in aprevious process batch. With such a design, the flow tubes 210 and thesupport 220 can be disposed as one piece, e.g., after single use, andthe other components of the flow sensor 200 can be reused. Compared withdisposing the whole flow sensor 200, this is more environmentallyfriendly and cost efficient.

FIG. 3 illustrates a tube length 315 of U-shape flow tubes 310, inaccordance with an embodiment. The flow tubes 310 (individually referredto as “flow tube 310”) are identical, and they can be an embodiment ofthe flow tubes 119 in FIG. 1. Each flow tube 310 includes two paralleltubular legs that are clamped by a support 320. The support 320 includesport extensions 330 (individually referred to as “port extension 330”)and isolation plates 340 (individually referred to as “isolation plate340”). Each tubular leg contacts an isolation plate 340 of the support320 at a contact point 350. The tube length 315 of the flow tubes 310 isa vertical distance from the tip 360 of the U to the contact point 350.

The tube length 315 affects the resonant frequency of the flow tubes310. Flow sensors within a single flow measurement system can have flowtubes of different tube lengths to mitigate cross-talk between the flowsensors. The tube length difference between two flow sensors can be 0.5mm or more. In some embodiments, the maximum tube length differencebetween any two flow sensors relates to the number of flow sensors inthe flow measurement system and a tube length design tolerance ofindividual flow sensors. For instance, in an embodiment where the tubelength design tolerance requires the tube length of an individual flowsensor to be in a range from 100 mm to 150 mm and the flow measurementsystem includes 11 flow sensors, the maximum tube length difference is 5mm.

FIG. 4 illustrates a wall thickness 415 of U-shaped flow tubes 410, inaccordance with an embodiment. The flow tubes 410 can be identical andcan be an embodiment of the flow tubes 119 in FIG. 1. Each flow tube 410is in a form of a tube. The wall thickness 415 is the thickness of thetube wall, e.g., the difference between the inner radius of the tube andthe outer radius of the tube.

The wall thickness 415 affects the resonant frequency of the flow tubes410. Flow sensors within a single flow measurement system can have flowtubes of different wall thicknesses to mitigate cross-talk between theflow sensors. The wall thickness difference between two flow sensors canbe 0.1 mm or more. In some embodiments, the maximum wall thicknessdifference between any two flow sensors relates to the number of flowsensors in the flow measurement system, a design tolerance for the flowtube outer diameter (e.g., the maximum threshold for the flow tube outerdiameter), and a design tolerance for the flow tube inner diameter(e.g., the minimum threshold for the flow tube inner diameter).

FIG. 5 illustrates attachments 510 mounted on U-shaped flow tubes 520,in accordance with an embodiment. The two flow tubes 520 are identical,and the two attachments 510 are identical. Each of the attachments 510(individually referred to as attachment 510) is mounted on one of theflow tubes 520 (individually referred to as flow tube 520) to add weighton the flow tube 520. With the add-on weight, the flow tubes 510 canhave a different resonant frequency due to the change in weight. In theembodiment of FIG. 5, the attachment 510 is in a form of a short tubethat encloses a portion of the flow tube 520 including the bottom of theU. The inner diameter of the attachment 510 is the same as or slightlylarger than the outer diameter of the flow tube 520. In otherembodiments, the attachment 510 can be in other forms, such as a pieceattached on the bottom of the U, etc. The attachment 510 may be mountedat different positions on the flow tube 520.

In some embodiments, the weight of the attachment 510 is at least 0.1gram, e.g., in a range from 0.1 gram to 1 gram. In a flow measurementsystem containing multiple flow sensors, one of the flow sensors mayhave no attachment mounted on it and the other flow sensors may haveattachments of different weights so that all the flow sensors havedifferent weights and different resonant frequencies from each other.Taking the flow measurement system 100 in FIG. 1 for example, in oneembodiment, the flow sensor 110 includes no attachment mounted on itsflow tubes 119, but the flow sensor 120 includes the attachments 510,and the flow sensor 130 includes attachments heavier than theattachments 510. The weight difference between any two of the flowsensors 110, 120, and 130 can be at least 0.1 gram so that the flowsensors 110, 120, and 130 have different resonant frequencies from eachother.

FIG. 6A illustrates a flow sensor 600 including a V-shaped flow tube610, in accordance with an embodiment. The flow sensor 600 also includestwo supports 620 (individually referred as “support 620”), a magnetassembly, and an enclosure. FIG. 6B illustrates a flow sensor system 650including the flow sensor 600, in accordance with an embodiment. Theflow sensor system 650 also includes a cradle 660 where the flow sensor600 can be mounted.

The cradle can be made of stainless steel. The cradle 660 maintains aposition of the flow sensor 600 and prevents impact of externalvibration on the flow sensor 600. The cradle can be made of metal, e.g.,stainless steel. The cradle 660 includes a coil assembly, which includessense coils 673 and 675 and a drive coil 677, and a locking assembly,which includes two latches 682 and two grooves 688.

The flow tube 610 has a V shape. It includes two ports 613 and 615 atopposite ends. A fluid can enter the flow tube from one of the two ports613 and 615 and exit from the other port. The fluid encounters a smallerpressure drop in the V-shaped flow tube 610, compared with a U-shapedflow tube. The flow tube 610 has a thin wall and small inner diameter.The thickness of the wall can be less than 1 mm, e.g., in a range from0.05 mm to 0.60 mm. The inner diameter of the flow tube 610 can be 0.10mm to 0.81 mm. Such dimensions make the flow tube 610 suitable formeasuring low flow rates, e.g., flow rates from 0.05 gm/min to 0.5gm/min. Also, the flow rate turndown of the flow sensor 600 (i.e., theoperation range of the flow sensor) can exceed 120 :1, which is betterthan typical flow rate turndowns.

As shown in FIG. 6B, each of the two ports 613 and 615 can be locked ina groove 688 of the locking assembly of the cradle by using a latch 682.The locking assembly can prevent the flow tube 610 from rotating. Insome embodiments, the flow tube 610 is fabricated by extruding a polymer(e.g., PEEK) to form a straight tube and then bending the tube into thedesired V-shape.

The two supports 620 in FIG. 6A provides structural support to the flowtube 610. Each support 620 has a form of a ring. Each support 620 clampsthe flow tube 610, and the flow tube 610 extends through the twosupports 620. The supports 620 can be fabricated by casting around theflow tube 610. Other fabrication techniques, e.g., injection molding,cannot form the supports 620 without deforming the flow tube 610. Insome embodiments, the supports 620 are identical.

The magnet assembly includes a drive magnet 642, a drive magnet mount644, two sense magnets 646, and two sense magnet mounts 648. The drivemagnet 642 is glued onto the drive magnet mount 644, and the sensemagnets 646 are glued to the sense magnet mounts 648, e.g., by usingLoctite M-31CL epoxy. The drive magnet mount 644 and sense magnet mounts648 are attached on the flow tube 610. The drive magnet 642 couples witha drive coil 677 of the coil assembly in the cradle 660 for driving theflow tube 610 to vibrate, e.g., at a fixed resonant frequency. The sensemagnets 646 couple with sense coils 673 and 675 shown in FIG. 6B togenerate two electrical signals indicating change in the vibration ofthe flow tube 610 due to Coriolis forces and the phase shift between thetwo electrical signals which corresponds to the mass fluid flow ratethrough the flow tube(s) 610.

The enclosure includes two halves 640 and 645. It encloses a portion ofthe flow tube 610, e.g., the portion between the supports 620, and themagnet assembly. In some embodiments, the flow tube 610, the supports620, and the magnet assembly (or the flow tube 610 and the supports 620)are integrated. For instance, they can be inserted into or removed fromthe enclosure as one piece. They can also be disposed as one piece aftersingle use. In some embodiments, the flow sensor 600 itself, includingthe enclosure, can be installed on or removed from the cradle 660 as onepiece and be disposed after single use.

FIG. 7 illustrates a tube length 715 of a flow sensor 700 including aV-shape flow tube 710, in accordance with an embodiment. An embodimentof the flow sensor 700 is the flow sensor 600 in FIG. 6. Part of theflow tube 710 is enclosed in a V-shaped enclosure 720. The flow sensor700 is mounted on a cradle 730. The tube length 715 is a distance fromthe bottom of the enclosure 720 to the top of the cradle 730 in the Ydirection.

The tube length 715 affects the resonant frequency of the flow sensor700. Flow sensors that operate within a single flow measurement systemcan have flow tubes of different tube lengths to mitigate cross-talkbetween the flow sensors. The tube length difference between two flowsensors can be 0.5 mm or more. In some embodiments, the maximum tubelength difference between any two flow sensors is determined by thenumber of flow sensors in the flow measurement system and a tube lengthdesign tolerance of individual flow sensors. For instance, in anembodiment where the tube length design tolerance design tolerancerequires the tube length of an individual flow sensor to be in a rangefrom 100 mm to 150 mm and the flow measurement system includes 11 flowsensors, the maximum tube length difference is 5 mm.

The tube length 715 can be determined based on an angle 740 of the V.V-shape flow sensors having different tube lengths may have differentangles. For instance, a V-shape flow sensor having a larger tube lengthhas a smaller angle compared with a V-shape flow sensor having a smallertube length.

FIG. 8 illustrates an attachment 810 mounted on a V-shaped flow tube820, in accordance with an embodiment. The attachment 810 adds weight onthe flow tube 820. With the add-on weight, the flow tube 820 can have adifferent resonant frequency due to the change in weight. In theembodiment of FIG. 8, the attachment 810 is in a form of a rectangularpiece that clamps the tip of the V. In other embodiments, the attachment810 can be in other forms, such as a short V-shape tube that encloses aportion of the flow tube 820. The attachment 810 may be mounted atdifferent position on the flow tube 820.

In some embodiments, the weight of the attachment 810 is at least 0.1gram, e.g., in a range from 0.1 gram to 1 gram. In a flow measurementsystem containing multiple flow sensors, one of the flow sensors mayhave no attachment mounted on it, another flow sensor may have theattachment 810 mounted on it, and yet another flow sensor may have anattachment heavier than the attachment 810.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the disclosure be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

What is claimed is:
 1. A process skid comprising: a mixing manifold; afirst flow path connected to the mixing manifold, and a first pump and afirst Coriolis flow sensor positioned along the first flow path, whereina first fluid flows through the first pump and the first Coriolis flowsensor and into the mixing manifold; a second flow path connected to themixing manifold, and a second pump and a second Coriolis flow sensorpositioned along the second flow path, wherein a second fluid flowsthrough the second pump and the second Coriolis flow sensor and into themixing manifold; and a third flow path connected to the mixing manifold,wherein a third fluid flows out of the mixing manifold, the third fluidcomprising a mixture of the first and second fluids; wherein the firstCoriolis flow sensor and the second Coriolis flow sensor have differentresonant frequencies.
 2. The process skid of claim 1 wherein the processskid is a biopharmaceutical or pharmaceutical skid.
 3. The process skidof claim 1 wherein the first and second Coriolis flow sensors aresterilizable by gamma irradiation.
 4. The process skid of claim 3wherein each of the first and second Coriolis flow sensors comprises atleast one flow tube and an enclosure that encloses the flow tube, andthe Coriolis flow sensors are sterilizable by gamma irradiation throughthe enclosure.
 5. The process skid of claim 3 wherein each of the firstand second Coriolis flow sensors comprises at least one stainless steelflow tube and a plastic enclosure that encloses the flow tube.
 6. Theprocess skid of claim 3 wherein each of the first and second Coriolisflow sensors comprises at least one flow tube and an enclosure thatencloses the flow tube, and the flow tube and enclosure are integratedand disposable as a single piece.
 7. The process skid of claim 1 furthercomprising a first cradle and a second cradle, wherein the first andsecond Coriolis flow sensors are disposable and are installed on andthen removed from the first and second cradles after a single use. 8.The process skid of claim 1 further comprising: a third Coriolis flowsensor positioned along the third flow path, wherein the first andsecond Coriolis flow sensors are closer to each other than to the thirdCoriolis flow sensor.
 9. The process skid of claim 1 wherein the firstand second flow paths are parallel to each other.
 10. The process skidof claim 1 wherein the first Coriolis flow sensor comprises a first flowtube and the second Coriolis flow sensor comprises a second flow tube,and a length of the second flow tube is different from a correspondinglength of the first flow tube, whereby a resonant frequency of thesecond flow tube is different from a resonant frequency of the firstflow tube.
 11. The process skid of claim 10 wherein a difference betweenthe length of the second flow tube and the corresponding length of thefirst flow tube is at least 0.5 mm.
 12. The process skid of claim 1wherein the first Coriolis flow sensor comprises a first flow tube andthe second Coriolis flow sensor comprises a second flow tube, and amaterial of the second flow tube is different from a material of thefirst flow tube, whereby a resonant frequency of the second flow tube isdifferent from a resonant frequency of the first flow tube.
 13. Theprocess skid of claim 1 wherein the first Coriolis flow sensor comprisesa first flow tube and the second Coriolis flow sensor comprises a secondflow tube, and a thickness of a wall of the second flow tube isdifferent from a thickness of a corresponding wall of the first flowtube, whereby a resonant frequency of the second flow tube is differentfrom a resonant frequency of the first flow tube.
 14. The process skidof claim 13 wherein a difference between the thickness of the wall ofthe second flow tube and the thickness of the corresponding wall of thefirst flow tube is at least 0.1 mm.
 15. The process skid of claim 1wherein the first Coriolis flow sensor comprises a first flow tube andthe second Coriolis flow sensor comprises a second flow tube, and anattachment is mounted on the second flow tube but not on the first flowtube, such that a weight of the second flow tube plus attachment isdifferent from a weight of the first flow tube without attachment,whereby a resonant frequency of the second flow tube is different from aresonant frequency of the first flow tube.
 16. The process skid of claim15 wherein a weight of the attachment is at least 0.1 gram.